March 16 — The Internet has become a crucial bridge for deployed troops and their loved ones, but the frequent contact also creates new worries about compromising military security.

“MIKE CAN’T EVEN say whether he’s busy today,” Gordon Warren said of his son, who fixes radar on the USS Nimitz, an aircraft carrier bound for the Mideast. “That could be construed as having a lot of problems with the radar.”

Warren doesn’t mind the restrictions. He appreciates a line or two saying his son is OK. He writes him daily and occasionally e-mails pictures. A colleague forwards jokes.

Soon after the ship left San Diego two weeks ago, Mike Warren’s former physics teacher in Bloomington, Ill., Debbie Voorhees, posted on a Nimitz bulletin board, “Keep that Radar running!”

“Chit chat and small talk can relieve a lot of tension,” Voorhees said.

E-mail and bulletin boards can’t replace phone calls or care packages, but they can help fill the gap.

“That one e-mail, you can save and read over and over until the next one comes,” said Marina Kubacki, whose husband recently left Fort Campbell, Ky., for Kuwait with the Army’s 101st Airborne Division.

On the USS Kitty Hawk, a closed-circuit television spot warns sailors not to talk about the carrier’s location, direction and speed. Other “no-no’s” include crew issues such as morale and weariness.

“The hardest thing about e-mail is being careful about what you say,” Mike Warren said by cell phone as the Nimitz stopped in Hawaii. “Sometimes it’s kind of hard to find stuff to talk about.”

Navy submarines monitor their sailors’ Internet use because of greater requirements for stealth. Elsewhere, restrictions and surveillance are left to individual commanders, who generally trust their rank-and-file.

First Lt. Joshua Rushing, a spokesman for the U.S. Central Command in Qatar, said few people have sensitive information to begin with.

And Army Lt. Gen. Peter Cuviello points out that if there is combat, key soldiers “won’t be doing e-mail anyway. They’ll be in tanks, Bradleys and artillery pieces.”

Unit commanders do occasionally cut off outbound access completely - and will again shortly before any attack.

To keep foes guessing, Navy vessels try to limit their electronic “leakage” from time to time, meaning sailors can get e-mail but not reply right away.

Steven Aftergood, senior research analyst at the Federation of American Scientists, said Internet breaches are low among security worries. The primary fear, he said, is not from hacking or interception but from recipients spreading messages further.

ACCESS VARIESInternet access and speeds vary from ship to ship, camp to camp.

Sailors generally get online through satellite links using computers in ship libraries or other public areas. On land, “morale tents” are lined with rows of Internet-enabled computers.

Some personnel use computers at their work stations. A few have laptops, but not all are allowed on military networks.

Specific applications like instant messaging are also sometimes barred for security reasons, though time zones are a greater problem.

When access is available to the troops, usage can be limited - 20 minutes here, an hour there - and lines can stretch for hours.

On the Kitty Hawk, for instance, only 10 of the 1,400 computers are available for e-mail. The carrier shares satellite bandwidth with other ships. The USS Constellation at one point had to ban video clips because they were using so much capacity.

Phones are available, but can get expensive - an AT&T prepaid calling card costs $20 for 20 minutes on the Nimitz.

Many find e-mail quicker and cheaper.

“If you can type fast, you can get a long letter written in 20 minutes,” said Pfc. James Bowers, 20, of Indianapolis, with the 101st Airborne in Kuwait. “When you call and get the answering machine, that sucks bad.” He’s been e-mailing an Internet-savvy teenage niece, figuring she could pass notes to others.

SUPPORT GROUPS GO ONLINEBack home, Internet support groups help families cope. Some Web sites have organized campaigns to write letters and send care packages or music CDs to the troops.

Many families are setting up online photo albums or journals known as blogs. Some units in the field have created Web pages. The Army even gives soldiers accounts to set up password-protected sites.

“Families worry a lot less,” said Brandon Rice, who kept a blog as an Army reservist in Afghanistan and Uzbekistan. “They can see our faces, what we were doing.”

Rice once mistakenly posted a photo of an airplane on his unit’s blog. Later, as its audience grew beyond friends and family, a network administrator suggested that he get the site approved, which he then did.

David Sherman, an Air Force health care administrator in Montana who regularly read Rice’s blog and writes his own, said security concerns leave soldiers talking about the mundane: “It’s dry. It’s dusty. They are serving prime rib.”

As dependency on the Net increases - the Pentagon suspended letter-writing campaigns because of anthrax fears - expectations grow, too.

Spouses going through first deployments get upset if they haven’t heard back within a few days, even though veteran military spouses know what it’s like to wait weeks or months, said Kim Modlin, who runs e-mail support groups from Germany and has a husband in the Mideast.

“It can be depressing,” she said, “when everyone around you said they’ve heard from their spouses.”

AP correspondents Kimberly Hefling with the 101st Airborne Division and Rohan Sullivan on the USS Kitty Hawk contributed to this story.